Most skin cancer is the result of exposure to ultraviolet radiation from the sun, which suppresses the skin’s immune system making people less able to fight off skin diseases such as cancer. But researchers in England have shown that a daily dose of omega-3 can partially counteract this effect, reducing an individual’s likelihood of developing skin cancer. The fatty acids have been shown to prevent cancer in mice, but this was the first time it was demonstrated in humans.

Two recent studies are refuting the claims of omega-3 enthusiasts that the fatty acid, which is produced mainly by algae and is found in the animals that eat them (like fish), is the ultimate “brain food.”

Anecdotal reports had suggested that these fatty acids, called omega-3 because they have a kink in their structure three bonds from the end of the carbon chain, could improve brain function for everyone from the elderly to the unborn. Vitamin supplements of fish oil have therefore been flying off the shelves.

People who eat lots of fish are less likely to develop dementia or cognitive problems late in life. Observational studies have also found that taking omega-3s during pregnancy can reduce postpartum depression and improve neurodevelopment in children. What’s more, animals with an Alzheimer’s-like condition are helped by docosahexaenoic acid (DHA), one of several omega-3 fatty acids. And DHA disappears from the brains of people with Alzheimer’s. [ScienceNOW]

In an Alzheimer’s study published in The Journal of the American Medical Association, researcher Joseph Quinn gave about 400 patients suffering from mild to moderate Alzheimer’s 2 grams of either omega-3 DHA or a placebo each day. After 18 months, none of the patients showed improvement of their Alzheimer’s symptoms.